Camilla, who has been a huge fan of the West Midlands-based drama charting the ups and downs of life in fictional Ambridge for many years, shared a message to editor Jeremy Howe.
It was read at a BBC reception in Birmingham, held in celebration of the anniversary.
The message, read by British actress Louiza Patikas who plays Helen Archer on the long-running show, said: "As one of your greatest fans, and sadly unable to join you this evening, I will be thinking of you all and raising a glass to mark over a quarter of a million minutes of Archers magic from the last 72 years.
"Thank you for bringing joy, companionship, laughter, tears, compassion and understanding to your audience across the globe.
"Here's to the next 20,000 episodes – and, let's hope, the end of Rob Titchener once and for all!"
Titchener, played by Timothy Watson, is an Archers villain and the coercive control he exercised over his wife Helen, led to her stabbing him in front of her five-year-old son Henry.
The character left Ambridge after failing in his attempt to kidnap his and Helen's son, but he recently made a reappearance on the show.
The Archers has been broadcast on BBC radio since 1951 and has clocked up more episodes than any other continuous drama serial in the world.
Although the soap opera is based in a fictional village, it has twice featured cameos from members of the real British royal family: Queen Elizabeth II's sister Princess Margaret, in June 1984, and Camilla in February 2011.
Princess Margaret appeared as the surprise guest at a fundraising fashion show for the NSPCC in the ballroom of Ambridge's local hotel Grey Gables, while Camilla appeared in her role as president of the National Osteoporosis Society as part of a special episode to mark the 60th anniversary of the show.
In 2021, Camilla hosted a reception for cast and crew to mark the 70th anniversary of the popular BBC Radio 4 show where she praised the programme for raising awareness of challenging topics such as homophobia, modern slavery, alcohol addiction, domestic violence and coercive control.
Similarly last year, the programme marked the death of the Queen with a specially-recorded scene, which heard two of the serial's longest-running characters, Lynda Snell and Lilian Bellamy, reminiscing about the Coronation of Elizabeth II in 1953.
The BBC reception celebrating the 20,000 episode of The Archers is being held where the show is recorded at Birmingham's Mailbox studios.